Field of the Disclosure
Aspects of the present disclosure are generally directed to an apparatus and method for draining aqueous humor from an anterior chamber of an eye to a location external or distal to the anterior chamber for reducing intraocular pressure and, more particularly, to an implantable apparatus for regulating intraocular pressure by directing a flow of the aqueous humor externally from the anterior chamber of the eye to an external or distal drainage site for reducing and regulating intraocular pressure.
Description of Related Art
Glaucoma is a group of chronic optic nerve diseases and a leading cause of irreversible blindness. The major risk factor in glaucoma is elevated intraocular pressure due to improper drainage of aqueous humor from the eye. Reduction of intraocular pressure is the only proven treatment to stop the progression of vision loss.
Standard glaucoma surgeries to reduce intraocular pressure, such as trabeculectomies and glaucoma drainage device implantation, tend to be lengthy and traumatic with unpredictable outcomes and complication rates of 20-60%. Implantable drainage devices function to drain excess aqueous humor from the eye, and installation of such a drainage device typically requires a surgical opening made in the sclera to reach the interior of the eye, in particular the anterior chamber or the posterior chamber. Some drainage devices may then be inserted into the interior of the eye for conducting the aqueous humor to the subconjunctival space (with such a device herein referred to as a subconjunctival shunt). In some instances, the aqueous humor may then be drained from the anterior chamber externally to the conjunctiva (with such a device herein referred to as an external shunt). However, there does not appear to be any commercially available externally-applied shunts.
A problem associated with subconjunctival shunts is potential scarring of the bleb in the subconjunctival space affecting its fibrous capsule formation around the outlet, which in many cases requires surgical revision that leads to additional risk of complications. Therefore, there is an ongoing search to identify and utilize alternate drainage sites to avoid many problems associated with bleb and fibrous capsule formations.
External shunts avoid bleb and fibrous capsule formation and the unpredictability of wound healing in the subconjunctival space. However, the outlet of an external shunt may be perceived by the patient as a foreign body, especially those that lie on the corneal surface. These shunts can also be displaced by local tissue motion or extruded by constrictive wound healing processes. In addition, external shunts can expose a mechanical conduit available to transmit microorganisms from the outside to the interior of the eye, potentially leading to retrograde infection.
All drainage devices implanted in the eye have the potential to clog from proteins or other substances in the aqueous humor. Clogging reduces permeability of the device and may lead to elevation of intraocular pressure compared to baseline. Moreover, the intraocular pressure may naturally vary or fluctuate due to changes in aqueous humor dynamics of the particular eye, regardless of the effect of a drainage device.
For the foregoing reasons there is a need for an improved drainage device for directing aqueous humor away from the anterior chamber of an eye for reducing and managing intraocular pressure.